I have a 56' ford f100 with power brakes. Always felt that the break were not right as the pedal always got really low to the floor. This past month, the master cylinder began leaking. Replaced it with a new one, which was a 1" bore master cylinder from a 79-81 Buick Riviera.
After bench bleeding and installing, vacuum bled the lines, the pedal could be pushed to the floor with my hand without the engine running.
First I thought the new master cylinder might be bad. To test it out I removed the rear brake line and plugged it. When I did so, I tried pressing on the brake pedal and there was almost not movement.
This has me thinking that there is something going on with the rear brakes. I have a 10lb residual in the line. I was also asked by the auto parts store if it was rear drums or disks so I got the mc for the drums.
I believe the drums brakes are adjusted properly as I can hear the pads drag on the drums and it is difficult to rotate the rear tires by hand.
Only thing I can think is that the rear flex line is ballooning, but would that cause such a drop in the pedal?
Any help or other ideas would be appreciated.

solidaxel

09-01-2011 12:13 AM

Considering how tight the rear shoes are on the drum there should not be much movement of the wheel cylinder, so with no resistance, soft rubber line, all of that movement could be in the rubber hose , and not expanding the shoes in the drum

MidnightFord

09-01-2011 08:59 PM

Learned something today. The port closest to the push rod is for the front brakes, correct?
That being the case, I only have the front brakes hooked up now and the pedal goes to the floor. Any ideas? The brakes are mounted below the cab. Years ago I put a 10# residual on what I thought was the rear brake line but is actually the fronts. It is still on there and there is no change in performance. Pedal still gets real low to floor.

Cape Cod Bob

09-01-2011 09:05 PM

go to this site. Very helpful. Get their catalog. Loaded with info on how to. Even call for tech advice.http://www.mpbrakes.com/ :welcome: